Classification of Tuna Freshness Phases Integration of E-Nose and Digital Colorimetry

Abstract

Traditional methods for evaluating tuna freshness are often constrained by human subjectivity, high costs, and destructive laboratory procedures. This presents a challenge to food safety, particularly in preventing toxic histamine accumulation and mitigating export rejections. This study investigates a rapid, non-destructive, and low-cost quality evaluation system for raw tuna using integrated modern sensor technologies. The system incorporates an electronic nose utilizing MQ-136 and MQ-137 gas sensors to monitor volatile hydrogen sulfide (H₂S) and ammonia (NH₃) emissions during open-air storage, combined with an integrated color sensor driven by a microcontroller architecture. Kinetic modeling confirmed that both NH₃ and H₂S rate constant (R²) of 0.82. Classified tuna quality into three phases: fresh (0-10 hour), semi-fresh (11-20 hour), and spoiled (21-30 hour). Concurrently, the microcontroller executed real-time visual classification based on specific Red-Green-Blue (RGB) range: fresh (172 < R < 184, 70 < G < 104, $89 < B < 129), semi-fresh (151 < R < 167, 32 < G < 64, 49 < B < 83), and spoiled (119 < R < 149, 0 < G < 28, 0 < B < 45).  This portable and objective sensing platform provides for high-speed, real-time quality control and safety in food industry.